All-speed-range propeller having stern fins

ABSTRACT

An all-speed-range propeller having stern fins comprises an all-speed-range propeller installed on a propelling shaft of a boat, and a plurality of stern fins installed between the all-speed-range propeller and a hull of the boat. When the all-speed-range propeller having stern fins is applied to the oblique boat on which the propelling shaft is disposed obliquely, the stern fins directly guide the water flow toward the all-speed-range propeller, so that the uneven inflow caused by the obliquely-designed propelling shaft can be conquered to promote the operating efficiency of the all-speed-range propeller.

1. FIELD OF THE INVENTION

The present invention relates to an all-speed-range propeller having stern fins.

2. DESCRIPTION OF THE RELATED ART

Currently, the propellers of NACA series or KCA series are only suited to the speed of the boat under 30 knots, and the propellers of supercaviating series are only suited to the speed of the boat above 30 knots. In order to conquer afore restrictions, the inventor of the present invention disclosed “ADVANCED FOIL DESIGN METHOD AND STRUCTURE FOR MULTI SPEEDS” of the Patent Publication No. US 2011/0059663 A1, “METHOD OF AN ALL-SPEED PROPELLER” of the Patent Publication NO. US 2012/0065942 A1, and “MARINE PROPELLER APPLICABLE TO ALL SPEED RANGES” of a U.S. patent application Ser. No. 13/324,589. These publications and application discloses an all-speed-range propeller that contains the advantages of the propeller of the supercaviating series when it is driven by a high speed, and the performance of the propeller will not be influenced when it is driven by a low speed. Thus, these propellers are suited to all speed ranges.

However, although such all-speed-range propellers are practical and popular in the market, the inventor finds out that the propelling shaft of the all-speed-range propeller is an oblique design. Herein, when the inflow angle of the all-speed-range propeller is over 5 degrees, the operating efficiency of the all-speed-range propeller is largely reduced. Accordingly, the inventor of the present invention endeavors to improve the all-speed-range propeller and bring out the present invention.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an all-speed-range propeller that is suited to an oblique propelling shaft of an oblique boat, and concurrently keeping the efficiency of the all-speed-range propeller.

The all-speed-range propeller having stern fins of the present invention is able to be installed on an oblique boat. Wherein, the oblique boat has a hull established along a horizontal line. At least one propelling shaft is disposed on the hull, and the propelling shaft is set with respect to the horizontal line by an included angle. The all-speed-range propeller having stern fins further comprises: an all-speed-range propeller is disposed on the propelling shaft, and a plurality of stern fins are installed surroundingly on the propelling shaft at intervals, between the hull and the all-speed-range propeller.

Accordingly, the all-speed-range propeller of the present invention is utilized on the oblique propelling shaft of the oblique boat. The stern fins guide the water flow to the all-speed-range propeller so as to conquer the uneven inflow caused by the oblique propelling shaft. Thereby, the operating efficiency of the all-speed-range propeller can be promoted, which preferably amends the problems existing in the current all-speed-range propeller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the present invention;

FIG. 2 is a partially enlarged sided view of the present invention;

FIG. 3 is a schematic view showing the operating performances of the present invention; and

FIG. 4 is a schematic view showing the comparison of the blades of the present invention while being driven.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a schematic view of the present invention and a partially enlarged sided view of the same are provided. An all-speed-range propeller 100 is provided for being installed on an oblique boat 200. Wherein, the oblique boat has a hull established along a horizontal line L. At least one propelling shaft 202 is disposed on the hull, and the propelling shaft 202 is set with respect to the horizontal line L by an included angle θ. The included angle θ formed by the propelling shaft 202 and the horizontal line L is between 6 degrees and 14 degrees. The all-speed-range propeller 100 having stern fins comprises:

an all-speed-range propeller 10 disposed on the propelling shaft 202 has a plurality of blades 11; the detailed structure of the all-speed-range propeller 10 has been disclosed before, thus hereby being omitted; and

a plurality of stern fins 20 installed surroundingly on the propelling shaft 202 at intervals, between the hull 201 and the all-speed-range propeller 10. Wherein, there are 3 to 7 stern fins 20 surroundingly established on the propelling shaft 202. The fin type of the stern fins 20 adopts a NACA 66 type. A height of the stern fins 20 is 0.5 to 1.5 times of a height of the blades 11 of the all-speed-range propeller 10. A distance between the stern fins 20 and the all-speed-range propeller 10 is 0.5 to 1.5 times of a radius of the blades 11 of the all-speed-range propeller 10. A camber direction of the stern fins 20 is the same as a rotating direction of the propelling shaft 202.

Referring to FIG. 3, a schematic view is showing the operating performances of the present invention. When the all-speed-range propeller 100 having stern fins is applied to the oblique propelling shaft 202 of the oblique boat 200, the stern fins 20 directly guide the water flow toward the all-speed-range propeller 10 so as to conquer the uneven inflow caused by the oblique propelling shaft 202. Namely, the disadvantage of an overlarge inflow angle is amended, and the operating efficiency of the all-speed-range propeller 10 is enhanced. Thus, the all-speed-range propeller 10 is now suited to the oblique boat 200. According to a practical test, when the speed of the boat is 40 knots and the included angle of the propelling shaft 202 and the horizontal line L is 10 degrees, the operating efficiency of the all-speed-range propeller 100 having stern fins can be enhanced 2 to 3%.

Further, referring to FIG. 4, a schematic view is showing the comparison of the blades of the present invention while being driven. According to a practical test, a static thrust of the all-speed-range propeller 10 having stern fins is enhanced to 40 newton, and the amplitude of vibration of the propeller in time of operating can be largely lessened. That is to say, the stern fins 20 not only promote the operating efficiency of the all-speed-range propeller 10 but stabilize the thrusting force of the propeller. Accordingly, the all-speed-range propeller 10 is not subject to fatigue. 

I claim:
 1. An all-speed-range propeller having stern fins being able to be installed on an oblique boat; wherein, said oblique boat having a hull established along a horizontal line; at least one propelling shaft being disposed on said hull, and said propelling shaft being set with respect to said horizontal line by an included angle; said all-speed-range propeller having stern fins further comprising: an all-speed-range propeller disposed on said propelling shaft having a plurality of blades; and a plurality of stern fins installed surroundingly on said propelling shaft at intervals, between said hull and said all-speed-range propeller.
 2. The propeller as claimed in claim 1, wherein, said included angle formed by said propelling shaft and said horizontal line is between 6 degrees and 14 degrees.
 3. The propeller as claimed in claim 1, wherein, a fin type of said stern fins adopts a NACA 66 type.
 4. The propeller device as claimed in claim 1, wherein, a height of said stern fins is 0.5 to 1.5 times of a height of said blades of said all-speed-range propeller.
 5. The propeller as claimed in claim 1, wherein, a distance between said stern fins and said all-speed-range propeller is 0.5 to 1.5 times of a radius of said blades of said all-speed-range propeller.
 6. The propeller as claimed in claim 1, wherein, 3 to 7 stern fins are adopted.
 7. The propeller as claimed in claim 1, wherein, a camber direction of said stern fins is the same as a rotating direction of said propelling shaft. 